Rectification column



Aug. 13, 1957 c. o. JONKERS EI'AL I 2,802,345

RECTIF'ICATION COLUMN 2 Sheets-Sheet 1 Filed June 17, 1954 NKERS ENSKOHLER 7 INVENTORS LIUS OTTO JO WILLEM LAUR NES VAN DER CORN E JACOBJOHAN BY 1 I dim m H A, A

Aug. 13, 1957 C. O. JONKERS ET AL RECTIFICATION COLUMN Filed June 17,1954 Q i l 2 Sheets-Sheet 2 INVENTORS CORNELIUSOTTO JONK S JACOB WlUlMLALRENS K LER JOHANNES VAN DER STER AGENT United States Patent Ofifice2,802,345 Patented Aug. 13, 1957 RECTIFICATION COLUMN Cornelius OttoJonkers, Jacob Willem Laurens Kiihler,

and Johannes van der Ster, Eindhoven, Netherlands, assignors, by mesneassignments, to North American Philips Company, Inc., New York, N. Y., acorporation of Delaware The invention relates to a rectification columnfor separating gaseous mixtures, this column comprising a boiling vesselfor the fraction having the highest boiling point, to which boilingvessel heat is supplied by means of a heat exchanger which alsowithdraws heat from the gaseous mixture to be fractionated. Therectification column has the feature that the heat exchanger comprises apart which is located in the boiling vessel and by means of which heatis supplied to the fraction having the highest boiling point and afurther part which is located outside the boiling vessel and which is inthermal contact with the gaseous mixture to be fractionated, these partsbeing in thermal contact with one another by Way of a support.

The heat exchanger hitherto frequently used in rectification columnscomprises, in general, a tube located in the boiling vessel throughwhich the gaseous mixture to be fractionated is conducted. In such casesit will be necessary to eliminate from the medium any contaminationsliable to separate out during cooling of the medium, before the mixtureis supplied to the heat exchanger, since, if these contaminations wereseparated out in the heat exchanger, the heat exchanger could be cloggedcornparatively soon. Cleaning of such a heat exchanger located in theboiling vessel gives rise to comparatively great difliculties.

In the heat exchanger according to the invention any impurities willsettle in the part located outside the boiling vessel, so that anycleaning may be carried out in a simpler manner.

In a preferred embodiment of the invention the part of the supportlocated outside the boiling vessel extends transversely to that wall ofthe boiling vessel which constitutes the partition between the two partsof the heat exchanger. In a further embodiment of the invention the partof the support outside the boiling vessel is provided with a pluralityof extensions with which the gaseous mixture to be fractionated is inthermal contact, the heat of the extensions being conducted away for atleast 20% by conduction through the support to the part of the heatexchanger inside the boiling vessel.

Consequently, the heat exchanger according to the invention, used'in arectification column, may be utilised successfully as an ice separator.In this case, it will in general be necessary to purify the medium priorto its supply to the heat exchanger, for example by conducting itthrough chemical substances binding the impurities. The rectificationcolumn according to the invention is then characterized in that agaseous mixture to be fractionated is conducted through the part of theheat exchanger located outside the boiling vessel, in which one or morecomponents are separated out by cooling, this (these) component(s)precipitating on at least one of the extensions of this part, so that inthe proximity of these extensions the composition of the medium isvaried and the temperature at which the component(s) can separate out,decreases, whilst by suitable choice of the structural parts of the heatexchanger the meantemperature of each of these extensions, viewed fromthe hot side of the heat exchanger, is at the most 20 C., preferably atthe most 10 C. higher than that of the next following extension and innormal operation of the heat exchanger the mean temperature of theextension at which the separationstarts is at the most 20 C., preferablyat the most 10 C. lower than the point of separation of that componentof the medium as it is supplied to the extensions. It has been found tobe desirable to decrease gradually the temperature of the medium to becooled, whilst the medium is to be brought into turbulence in a mannersuch that all particles of the medium contact as frequently as possiblewith the walls of the heat exchanger. If this were not the case, iceparticles could already be formed in the gas, consequently before themedium has come into contact with the extensions; it is diificult forthe ice separator to collect all these ice particles, which are carriedalong by the medium.

In the heat exchanger described above only after a comparatively longtime such a quantity of solid substance will have been separated out onthe extensions that it is necessary to remove it. This may for examplebe carried out by heating the heat exchanger so that the solid substancewill be volatilized or become liquid. In order to cause the extensionsof the support section lying outside the boiling vessel to adopt therequired temperature, the support in a further embodiment of theinvention has parts of different heat resistance. The heat exchangeraccording to the invention may be used not only for freezing outimpurities but also for further cooling of the medium from which thecomponent(s) has (have) been separated. For this purpose the heatexchanger has the feature that the support section lying outside theboiling vessel is provided with a plurality of extensions, on which thecomponent(s) separate out and with a plurality of extensions by means ofwhich the medium, from which the component(s) has (have) been separatedis further cooled.

In a further embodiment of the invention the part of the support locatedoutside the boiling vessel is provided with at least two groups ofextensions, serving for separating out one or more components for thecase in which the said part of the heat exchanger is traversed by agaseous mixture containing a plurality of components to be separated andhaving different separation ranges; at one group of extensions mainlythe component(s) of one separation range and at the other group ofextensions mainly the component(s) of the other separation range is(are) separated out. The extensions of one group have in succession atemperature difference of not more than 20 0., preferably not more than10 C.

Since, in general, between the separation ranges a comparatively greattemperature difference will prevail, it is advantageous, in accordancewith a further feature of the invention to provide between the twogroups of extensions a' further group of extensions, serving mainly forcooling the medium. With this further group of extensions the aforesaidtemperature diiferences between the extensions need not be taken intoaccount, since no ice or only a small quantity of ice will be separatedout at these extensions. For the same reason the extensions may bearranged comparatively close to one another, so that this section willoccupy comparatively little space. According to a further feature of theinvention the extensions of the various groups are arranged in closerows behind one another. Thus the temperatures of the heat exchangervary little with the quantity of medium passing through it.

The desired temperatures of the extensions may be obtained byconstructing the support in a manner such that its parts have therequired heat resistances. This heat resistance may be obtained byproviding the desired dimensions, for example thicknesses or lengthsfor" the may have relatively different heat resistances.

support or by constructing the support from a special material. However,as an alternative in a further embodiment of the invention, at leastsome of the extensions In this case the heat resistance of the supportneed not fulfil particular requirements.

The heat exchanger may be constructed in various ways. In one embodimentof the invention the part of the support located outside the boilingvessel is provided with extensions, constructed in the form oftransverse partitions, bounding spaces between the hot side of the heatexchanger and the cold side thereof, these spaces communicating with oneanother through apertures, so that the medium can flow through theseapertures from the spaces of the hot side of the exchanger to the coldside thereof. In this embodiment it is desirable for the apertures to besuch that the medium traversing this part of the heat exchanger is setturbulating, so that the medium contacts frequently and intensively withthe extenstarts.

The desired turbulence may be obtained by providing the part of the heatexchanger outside the boiling vessel with a wall at a certain distancefrom the support, the support being provided with extensions in the formof transverse partitions apertures being left, between these partitionsand the wall.

In a further advantageous embodiment of the invention that part of theheat exchanger which is located outside the boiling vessel isconstituted by a support and a wall spaced apart therefrom by a certaindistance, the support being provided with transverse partitionsextending up to the wall, apertures being provided in these transversepartitions. In a further embodiment of the invention the apertures ineach transverse partition are preferably located at least partlyopposite a wall portion of theadjacent transverse partitions. In thismanner, in particular, an intensive turbulence of the medium is ensured.

In a further embodiment of the invention the part of the heat exchangerlocated outside the boiling vessel is also in thermal contact with atleast one of the vapour fractions conducted away from the rectificationcolumn.

This may for example be the fraction having the lowest boiling point.

If the column is used for producing nitrogen, at least part of thevapour fraction conducted away from the collumn having the highestboiling point will, in accordance with one embodiment of the invention,be in thermal contact with the part of the heat exchanger locatedoutside the boiling vessel.

A structurally simple system is obtained, if in accordance with afurther embodiment of the invention, the support is constituted by atube open at both ends and taken through the bottom of the boilingvessel, that end of the tube which is located in the boiling vesselprojecting over the normal liquid level.

In order that the invention may be readily carried into effect, it willnow be described with reference to the accompanying drawing, which showsdiagrammatically a few embodiments.

Figs. 1 and 2 show a gas fractionating system, provided with arectification column.

Fig. 2 is a cross-sectional view taken on the line IIII of Fig. 1.

Fig. 3 shows part of the heat exchanger used with the rectificationcolumn, the support thereof being surrounded by a wall, apertures beingleft between the extensions and the wall.

In the embodiment shown in Fig. 4 a few of the extensions of this heatexchanger have different heat resistances.

The system shown in Fig. 1 comprises a rectification column 1; thiscolumn has a filling 2 of for example so-called Raschig rings. At thebottom the column is provided with a boiling vessel 3, containing aquantity of the fraction having the highest boiling point in the liquidstate. The boiling vessel 3 has a bottom 4, through which a tubularsupport 5 is taken. This support is secured in thermally conductivemanner to the bottom of the boiling vessel. The support has wallportions 6, 7 and 8 of different thicknesses and both on the inner sideand on the outer side the support is provided with extensions, forexample vanes. The inner side is provided with extensions 9, providedwith apertures 10 and 11, as is evident from Fig. 2. The outside of thewall portion 6 of the support is provided with extensions 12; the wallportion 7 has the extensions 13 and the wall portion 8 has theextensions 14. All these extensions are provided with apertures 15,which are in staggered positions in successive extensions. The bottom ofthe boiling vessel is provided with extensions arranged concentricallyabout the support 16. The support 5 communicates at the lower side witha duct 17 and on the top side the support extends in the boiling vesselto such an extent that it projects over the normal liquid level in thisvessel. The part of the support located outside the boiling vessel issurrounded by a wall 18, having heat-insulating properties. This wall isprovided with two supply ports 19, communicating with a duct 2t and withan exit port 21, communicating with a duct 22, which communicates withthe gas fractionating portion of the column. The duct 20 comprises apump 23.

At the top the column communicates through a duct 24 with a cold-gasrefrigerator 25, which communicates moreover through a duct 26 with thecolumn. The coldgas refrigerator has an outlet duct 27 and is driven byan electric motor 28.

The system operates as follows. The medium, for example air to befractionated is supplied with the aid of the pump 23 through the duct 20in succession to the spaces between the extensions 14, 13 and 12. Owingto the frequent contact of the medium with the extensions 14 the watervapour contained in the air is frozen out on these extensions. Theseparation range extends to about C. At the extensions 13 thetemperature of the medium is further decreased to about -'140 C. and inthe part 12 the air is cooled from 140 C. to for example l82 C. Thecarbon acid then precipitates on the extensions 12. The extensions ofthe parts 14 and 12 are spaced apart by a comparatively great distanceand between the successive extensions of each group prevails acomparatively small temperature difference of for example 8 C. Thistemperature ditference is obtained by constructing the support fromparts having different heat resistances.

The air which is purified and the temperature of which is decreased issupplied through the duct 22 to the column I. This column isconstructed, for example in the form of a so-called single column andoperates under atmospheric or substantially atmospheric pressure. In thecolumn the air is fractionated. In the boiling vessel 3 of the column isproduced a substantially constant quantity of the liquid fraction havingthe highest boiling point, in this case oxygen. Liquid oxygen flows fromthe'column and evaporates in the boiling vessel. Part of the vapourrises upwards in the column and a further part is conducted away throughthe tubular support 5 and the duct 17. Inside the support 5 the latterpart of the vapourous oxygen is in thermal contact with the air to befractionated rising upwards outside the support. In this embodimentabout 70% of the cold withdrawn from the air Will serve to heat thisoxygen, whilst 30% is supplied through the support to the oxygen in theboiling vessel, the oxygen thus evaporating.

In the upper part of the column the fraction having the lowest boilingpoint, in this case, the nitrogen is in the vapour state. The vapour isconducted through the duct 24 to a cold-gas refrigerator 25. By means ofthe coldproduced by this cold-gas refrigerator the nitrogen is condensedand the condensate is supplied, partly as m caw-s reflux,-through vtheduct 26 to the column and partly collected through the duct 27. Thecoldgas refrigerating machine described above may, asan alternative, betermed a refrigerating machine operating on the reversed hot-gas engineprinciple. By meansof such a machine, described for example in Dutchpatent application N0. .1 60,452, very low temperature, for example of200 C. and even lower temperature may be obtained in one step.

The heat exchanger described above, in which the medium to be cooled andto be fractionated doesnot traverse the boiling vessel, may be used alsowith columns of different kind, for example with the so-called doublecolumns.

If the exchanger is filled after some time completely with deposits ofimpurities, the ice may be removed in a simple manner by scraping afterremoval of the sheath 18. As an alternative the ice may be removed byheating the heat exchanger.

In the embodiment shown in Fig. 3 the part of the heat exchanger locatedoutside the boiling vessel comprises a support 30, provided with annularextensions 31. These extensions are surrounded by a wall 32, havingheat-insulating properties. The extensions 31 do not extend entirely upto the wall 32, so that apertures 33 are left. The medium to be cooledis supplied from below through the port 34 and the cooled medium can beconducted away from below through the duct 35. The support 30communicates with the boiling vessel of a rectification column. Heat isconducted away from the medium flowing along the extensions through theextensions and the support to this boiling vessel. On the inner side ofthe support 30 provision is made of vanes 36, with which the gaseousfraction having the highest boiling point and flowing from the boilingvessel is in thermal contact. This heat exchanger operates in a mannercompletely similar to that of the heat exchanger described above.

Fig. 4 shows a heat exchanger in which the extensions have relativelydifferent heat resistances. In this embodiment a support 40 has constantheat conductivity and the heat exchanger comprises two parts, i. e. part41 having extensions 42 and part 43 having extensions 44. The parthaving the extensions 42 serves for separating out a component and thepart having the extensions 44 is only used for further cooling of themedium. The extensions 42 and 44 are provided with apertures 45 and 46respectively and with parts 47 and 48 respectively having each adefinite heat resistance. This heat resistance is such that the relativetemperature difierence of the extensions 42 are comparatively small. Theparts 47 and 48 are located in a layer of heat-insulating materialapplied to the support 40. The extensions are surrounded by a sheath 50having heat-insulating properties. The medium to be cooled and purifiedis supplied through the apertures 51 to the heat exchanger and isconducted away through the duct 52.

What is claimed is:

1. A rectification column for separating gaseous mixtures comprising aboiling vessel for the fraction having the highest boiling point, a heatexchanger for supplying heat to the liquid in said boiling vessel fromthe gaseous mixture to be fractionated, said heat exchanger having ahollow support member, and said heat exchanger being provided with afirst part located in said boiling vessel through which heat is suppliedto the fraction having the highest boiling point, and a second partincluding a plurality of extensions extending substantially transverselyto the flow of said gaseous mixture located outside of said boilingvessel and in thermal contact with the gaseous mixture to befractionated, said first and second parts being connected with oneanother and passing through the bottom of said boiling vessel.

2. A rectification column as set forth in claim 1 fur ther comprising apartition wall separating the first and second parts of said heatexchanger, and said support member being positionedsubstantiallytransversely to said partition wall. i

3. A rectification column as set forth in claim 1 wherein said secondpart includes a plurality of extensions being in thermal contact withthe gaseous mixture to be fractionated, and at least 20% of the heat ofsaid extensions being conducted away through said support member to thefirst part of said heat exchanger.

4. A rectification column for separating gaseous mix; tures comprising aboiling vessel for the fraction having the highest boiling point, a heatexchanger for supplying heat to the liquid in said boiling vessel fromthe gaseous mixture to be fractionated, said heat exchanger having ahollow support member, and said heat exchanger, being provided with afirst part located in said boiling vessel through which heat is suppliedto the fraction having the highest boiling point, and a second partlocated outside of said boiling vessel and in thermal contact with thegaseous mixture to be fractionated, said first and second parts beingintegral with one another and passing through the bottom of said boilingvessel, both the first and second parts of said heat exchanger beingprovided with extensions, the gaseous mixture to be fractionated beingconducted along the extensions of said second part and having at leastone of said components being separated out by cooling, the meantemperature of each of said extensions being at the most 20 C. higherthan the successive extension as viewed from the hot side of said heatexchanger while in the normal operation of the heat exchanger the meantemperature of one of said extensions is not more than 20 C. lower thanthe point of separation of said components of the mixture as supplied tosaid extensions.

5. A rectification column as set forth in claim 4 wherein the portion ofthe support member located outside said boiling vessel includes aplurality of parts of diiferent heat resistance.

6. A rectification column for separating gaseous mixtures comprising aboiling vessel for the fraction having the highest boiling point, a heatexchanger for supplying heat to the liquid in said boiling vessel fromthe gaseous mixture to be fractionated, said heat exchanger having ahollow support member, and said heat exchanger being provided with afirst part located in said boiling vessel through which heat is suppliedto the fraction having the highest boiling point, and a second partlocated outside of said boiling vessel and in thermal contact with thegaseous mixture to be fractionated, said first and second parts beingintegral with one another and passing through the bottom of said boilingvessel, said support member having a portion located outside saidboiling vessel being provided with a first plurality of extensions onwhich at least one of the components of said gaseous mixture isseparated out, and a second plurality of extensions by means of whichsaid component which has been separated out is further cooled.

7. A rectification column as set forth in claim 6 wherein said portionof said support member located outside said boiling vessel is traversedby said gaseous mixture containing a plurality of components havingdifierent separation ranges, at least two groups of extensions scouredto said support member for separating out at least two componentswhereby the components of one separa tion range are separated out on oneof said groups of extensions and the components of another separationrange are separated out on another group of extensions.

8. A rectification column as set forth in claim 6 further comprising athird group of extensions for cooling said gaseous mixture, said thirdgroup being located between said other two groups of extensions.

9. A rectification column as set forth in claim 6, wherein the groups ofextensions are arranged in superposed relationship.

10. A rectification column as set forth in claim 6 7 wherein at least acertain number of said extensions have d ifierent heat resistances.

11 A rectification column as set forth in claim 6 wherein the secondpart of said heat exchanger is provided with apertured extensions in theform of trans verse partitions bounding spaces from the hot side of theheat exchanger to the cold side'thereof, said spaces being incommunication with one another through said apertures.

12. A rectification column for separating gaseous mixtures comprising aboiling vessel for the fraction having the highest boiling point, a heatexchanger for supplying heat to liquid in said boiling vessel from thegaseous mixture to be fractionated, said heat exchanger having thegaseous mixture to be fractionated, said first and 20 second parts beingintegral with one another and passing through the bottom of said boilingvessel, said second part of the heat exchanger being provided with awall spaced apart from said support member, and said support memberbeing provided with extensions constructed in the form' ofstransversepartitions whereby a plurality of openings remain between saidpartitions and saidwall. 13. A rectification column as setforth in claim12 wherein said second 'part of the heat exchanger is constituted by asupport member anda wall spaced apart therefrom,- said support memberbeing provided with transverse pa'rtitions extending to said wall andsaid partitions being provided with apertures.

14. A rectification column as set forth in claim 12 wherein said secondpart of the heat exchanger is constituted by asupport member and a wallspaced apart therefrom, said support member being provided withtransverse partitions extending to said wall and said partitions beingprovided with non-aligned apertures,

References Cited in the file of this patent UNITED STATES PATENTS773,927 Cleveland Nov. 1, 1904 1,132,617 Rector Mar. 23, 1915 1,163,423Lilenfeld Dec. 7, 1915 2,494,304 McMahon Jan. 10, 1950

1. A RECTIFICATION COLUMN FOR SEPARATING GASEOUS MIXTURES COMPRISING ABOILING VESSEL FOR THE FRACTION HAVING THE HIGHEST BOILING POINT, A HEATEXCHANGER FRO SUPPLYING HEAT TO THE LIQUID IN SAID BOILING VESSEL FROMTHE GASEOUS MIXTURE TO BE FRACTIONATED, SAID HEAT EXCHANGER HAVING AHOLLOW SUPPORT MEMBER, AND HEAT EXCHANGER BEING PROVIDED WITH A FIRSTPART LOCATED IN SAID BOILING VESSEL THROUGH WHICH HEAT IS SUPPLIED TOTHE FRACTION HAVING THE HIGHEST BOILING POINT, AND A SECOND PARTINCLUDIND A PLURALITY OF EXTENSIONS EXTENDING SUBSTANTIALLY TRANSVERSELYTO THE FLOW OF SAID GASEOUS MIXTURE LOCATED OUTSIDE OF SAID BOILINGVESSEL AND IN THERMAL CONTACT WITH TTHE GASEOUS MIXTURE TO BEFRACTIONATED, SAID FIRST AND SECOND PARTS BEING CONNECTED WITH ONEANOTHER AND PASSING THROUGH THE BOTTOM OF SAID BOILING VESSEL.